A New Portable AC Power Source for Testing High Voltage Power Cables

High voltage power cables are difficult to energise under test conditions, due to their high reactive power requirements. Such energisation is essential, however, if cables and other high voltage capacitive components are to be field tested after installation or subject to condition monitoring procedures. In the past this problem has been avoided either by the use of dc, or testing at very low frequencies. Both the techniques do not relate even closely to service conditions, however, and the use of dc can result in damage to the equipment under test. More recently oscillating wave and pulsed resonant systems have been proposed but such test equipment is complex and expensive. Power frequency ac remains the preferred option. A novel ac mains frequency test set has been developed, incorporating a fixed iron-cored, air-gapped dual reactor, which together with switched capacitors, provides voltage transformation and an almost continuously variable amount of leading reactive power, allowing cables and other capacitive test objects to be tested in the field without the need to supply the reactive power from the mains. This paper describes the new test equipment and results of laboratory trials.